WASHINGTON — Senate Democrats deflected an initiative by Republicans yesterday that would have forced US and Russian negotiators to reopen an arms treaty reducing stockpiles of nuclear warheads.
But the 37-59 vote against an amendment by Senator John McCain, Republican of Arizona, exposed doubts about whether President Obama can win Senate ratification of the treaty before a new, more Republican Congress assumes power in January.
Treaties require a two-thirds majority of those voting in the Senate, or 67 votes if all 100 senators vote.
Led by McCain, Obama’s GOP opponent in the 2008 presidential election, Republicans tried to strike words from the treaty’s preamble that they say would allow Russia to withdraw from the pact if the United States developed a missile defense system in Europe.
The treaty is a foreign policy priority for Obama, who signed it in April with Russian President Dmitry Medvedev.
It would limit each country’s strategic nuclear arsenal to 1,550 warheads, down from the current ceiling of 2,200, and establish a system for monitoring and verification. US weapons inspections ended a year ago with the expiration of the 1991 arms control treaty.
Obama used his weekly radio and Internet address yesterday to call for ratification.
He also tried to allay GOP doubts with a letter yesterday to Senate minority leader Mitch McConnell, Republican of Kentucky, pledging to carry through with planned US missile defense facilities in Romania and Poland that would be capable of intercepting a missile from Iran aimed at the United States.
The treaty has received the backing of current and former military and national security officials, as well as former Republican President George H.W. Bush.
Democrats said a reference in the treaty’s preamble on missile defense systems is nonbinding and has no legal authority. In his letter, Obama said the United States disagrees with Russian statements about the threat that a missile defense poses to the strategic balance between the two countries.
“If you change it, it requires this treaty to go back to the Russian government, and then we don’t have any treaty,’’ said Senator John F. Kerry, the Massachusetts Democrat who chairs the Senate Foreign Relations Committee. Republican critics said Russia is using the treaty to continue its opposition to a US missile defense shield.